1. Field of the Invention
This invention relates generally to electric cigar lighters of the type commonly employed in automotive or recreation vehicles, and more particularly to specialized electrical connector constructions for energizing such lighters.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97-1.99
The present invention relates more particularly to improvements in the cigar lighter receptacle construction illustrated and described in assignee's expired U.S. Pat. No. 3,532,849 dated Oct. 6, 1970, issued to L. Horwitt, and entitled BIMETAL SHUNT FOR ELECTRIC CIGAR LIGHTER. Reference is specifically made to the embodiment of FIG. 4, and that of FIG. 5 of this patent.
The copending application referred to above, in the names of Donald J. Mattis and Ali El-Haj, discloses one approach constituting an improvement over the prior patented construction.
The following patents are hereby made of record and are believed to constitute a sampling of existing prior art in the particular field to which the present invention relates:
U.S. Pat. Nos.: 2,224,034, 2,248,402, 2,256,876, 2,258,989, 2,262,484, 3,012,120, 3,424,414, 3,462,721, 3,818,179, 3,863,047, 3,870,857, 3,892,944, 3,904,848, 4,498,726, 4,580,856, 4,650,962, 4,669,185, 4,713,017, 4,713,733, 5,044,993, 5,116,233.
U.S. Pat. No. 3,532,849, FIGS. 4 and 5, discloses cigar lighter constructions incorporating bimetal shunts disposed in adapter shells (22, 22') mounted at the rear of a lighter socket. In such constructions, controlled flexing of the bimetal occurs unless an overheat condition arises in the socket, such as that resulting from a short circuit in either the socket or the removable ignitor unit. In the event of malfunction, the bimetal flexes sufficiently to electrically contact the inner surface of the shell, thereby shorting the hot lead to ground, and purposely blowing an in-line fuse so as to minimize the possibility of a fire.
The concept of the bimetal shunt circuit in a cigar lighter socket has been widely accepted since the advent of this patent, and devices embodying the basic concept thereof have, as a result, enjoyed great commercial success over the years, having been utilized in millions of automotive vehicles and spanning a period of more than two decades.
Particular reference is made to the following three patents:
1. U.S. Pat. No. 3,012,120 discloses an in-line bimetal circuit breaker for installation at the rear of a cigar lighter socket. As shown, only the "hot" electrical circuit is controlled; the ground side of the circuit remains intact after the breaker opens. As opposed to U.S. Pat. No. '849 discussed above, this patented construction did not "shunt" the hot side of the circuit during an overheat condition. Instead, it effectively "interrupted" the circuit, as in the case of a fuse or circuit breaker, and once such an interruption occurred, the device was intended to be removed and discarded, and a substitute unit installed. The device retrofitted to existing cigar lighter base constructions, as stated in col. 3, line 25 of the patent.
2. U.S. Pat. No. 4,498,726 illustrates and describes a connector for a cigar lighter socket of the kind having a bimetal safety shunt similar to that of U.S. Pat. No. '849 identified above. The current carrying leads for both the hot and ground sides of the cigar lighter circuit are embedded in a molded plastic or rubber plug, and the plug is adapted to be pushed onto the central terminal stud of the base, and in addition, to make electrical contact with a screw shell carried by the base. In this construction, the bimetal shunt is a part of the cigar lighter socket per se.
3. U.S. Pat. No. 3,462,721 illustrates and describes a circuit breaker for a cigar lighter, in the form of a capsule-like enclosure disposed at the rear of the lighter socket, and containing a bimetallic circuit-breaker type element. The breaker element is adapted to open the hot side of the circuit in the event of overheating of the socket or plug as a consequence of malfunction. Provision is made for insertion of an elongate rod through the socket from the front, to access the interior of the enclosure and enable the breaker mechanism to be re-set, following actuation.
Referring now to others of the patents listed above, three show another form of cigar lighter which has been in widespread use in this country, for at least 15 years. In particular, U.S. Pat. Nos. 3,870,857; 3,892,944; and 3,904,848 contain generally similar disclosures which describe cigar lighter structures that are especially adapted for manufacture and assembly by means of automated equipment. At the time of issuance of these patents, the disclosed lighters were referred to by the assignee corporation, as "New Generation Lighters", because of the advances that had been made with respect to economy, ease of assembly, low failure rate, and the ability to mass produce them in large quantities.
U.S. Pat. No. 5,116,233 discloses a cigar lighter construction utilizing a modified form of bimetal shunt, somewhat similar to that of U.S. Pat. No. '849 noted above. In this patented design, the bimetal shunt is disposed inside the lighter socket, and is indicated at (17). Overheating of the pull-out igniting unit (not shown), or of the socket itself results in the bimetal contacting the inner surface of the metal socket wall (18), in turn causing an in-line fuse (not shown) to blow and thus minimize potential fire hazard.
The remaining patents mostly deal either with bimetal circuit controllers, or else with various terminal configurations associated with known cigar lighters and which were designed to facilitate making electrical connection thereto. These are briefly discussed hereinbelow, in chronological order.
U.S. Pat. No. 2,224,034 shows an early lighter design employing a bimetal element that is utilized solely as a releasable, non-current carrying clip which is engaged by a heating element cup when the lighter is actuated. One side of the electrical circuit was established through the metal socket of the lighter, while the hot side (stud 28, FIG. 1) accepted a crimp-type lug connected to an electrical lead of the wiring harness (not shown) of the vehicle's electrical system.
U.S. Pat. No. 2,248,402 illustrates another type of lighter construction in which a bimetal carried in the socket of the device is employed to release a latch that holds the ignitor plug as it is being energized. As in the patent of the previous paragraph, the bimetal itself is electrically out of the circuit, and merely functions to sense that a predetermined heat level has been attained by the heating element of the ignitor plug.
U.S. Pat. No. 2,256,876 illustrates a cigar lighter construction employing two bimetals, one to control latching and release of a spring-biased ignitor plug, and a second bimetal which, in the embodiment of FIG. 1, presses against the first with variable pressure depending upon the ambient temperature prevailing at any particular time. The objective is to minimize undesirable fluctuations in the operation of the first bimetal latch which would otherwise result from changes in its "starting" position due to ambient temperature variations. This patent was cited against U.S. Pat. No. 3,863,047, discussed below.
U.S. Pat. No. 2,258,989 illustrates a temperature sensor plug of especially compact design and which incorporates a bimetal member having multiple reverse bends to the end that changes in temperature cause deflection of the various branches of the bimetal in a manner wherein they are cumulative, in order to obtain maximum deflection and sensitivity over the range of temperatures being monitored. This patent was cited against U.S. Pat. No. 5,116,233 discussed above and which related directly to a bimetal shunt for a cigar lighter.
U.S. Pat. No. 2,262,484 illustrates an automatic cigar lighter having a disk-like bimetallic element which is disposed exteriorly of the socket of the lighter, and which is mechanically flexed by insertion of the ignitor plug, to close external switch contacts. Upon experiencing heat from the heating coil of the ignitor plug, the bimetallic element reverses its curvature and opens the contacts. The bimetallic element itself is separate from the current carrying part of the circuit, and as a result carries no current per se.
U.S. Pat. No. 3,424,414 illustrates a known cigar lighter receptacle of a type which employed the usual bimetallic latching fingers for engagement with a heating element cup of an ignitor plug. This patent was cited against U.S. Pat. No. '849 noted above.
U.S. Pat. No. 3,818,179 discloses a cigar lighter of a type having conventional internal bimetallic fingers which engage a heating element cup of an ignitor plug, and the socket of which has a rearwardly extending, generally cylindrical terminal post (27) for connection to a source of power, not shown. The receptacle configuration adapted to mate with this post is similarly not shown.
U.S. Pat. No. 3,863,047 describes a cigar lighter having incorporated therein a bimetal shunt adapted to respond to overheating within the socket by shifting against a plate connected to the hot terminal, to blow a fuse and minimize potential fire hazard. In one embodiment, the bimetal is carried by the ground side of the cigar lighter circuit, and is arranged to bridge the hot side of the circuit upon experiencing overheating. In a second embodiment, the bimetal is carried by the hot terminal, and is arranged to contact the inner surface of the cigar lighter socket upon experiencing overheating therein.
U.S. Pat. No. 4,580,856 discloses a composite clamp shell for a cigar lighter, constituted of two pieces and including an integral spade lug type terminal for connection to the ground side of an electric circuit, as by means of a grounding push-on type receptacle. U.S. Pat. No. 4,669,185 contains a similar disclosure, having been a Divisional Application based on the Application which matured into U.S. Pat. No. 4,580,856.
U.S. Pat. No. 4,713,017 illustrates and describes an electrical power outlet having a configuration somewhat similar to that of an electric cigar lighter socket. The rear of the socket contains two flat electrical terminals for connection to an electrical circuit.
U.S. Pat. No. 4,713,733 discloses a cigar lighter having a socket with two rearwardly-extending spade lugs for connection to an electrical receptacle (not shown).
U.S. Pat. No. 5,044,993 illustrates a power outlet construction comprising a socket formation having rearwardly extending contacts in the form of flat terminals, one of which is integral with the socket formation of the cigar lighter, having been stamped out therefrom. The resulting end portion of the one terminal is folded back upon itself, to form a contact terminal comprising a double thickness of metal, for improved strength.
While the devices disclosed in the patents noted above have in some circumstances met with commercial success, there is a continuous need to reduce overall manufacturing costs, including steps toward either minimizing or eliminating manual labor. In many of the patented structures, this objective of cost has not been adequately addressed.
Currently there exists a pronounced trend toward use of plastics in the automotive field, especially in the passenger compartment; accordingly, special attention must be given to potential sources of heat and/or fire. In some of the patented cigar lighter constructions employing a bimetal shunt, the bimetal was exposed at the rear of the socket. When overheating occurred, resulting in actuation of the bimetal shunt, arcing at the point of contact between the bimetal and its surrounding grounded conductor was considered somewhat of an electrical hazard.
Also, most prior lighter designs utilized specially configured connectors for energizing the cigar lighter through the socket. Until recently, relatively little attention was given toward standardization of the socket structures and their terminals, and as a consequence, a multiplicity of divergent socket designs have been devised and utilized over the years.